Polyolefin stabilized with an alkyl naphthoate and a heat stabilizer



United States Patent 3,218,277 POLYOLEFIN STABILHZED WITH AN ALKYLNAPHTHOATE AND A HEAT STABILIZER Eugene I... Ringwald and Cilton W.Tate, Cary, Nil,

assignors to Monsanto Company, a corporation of Delaware No Drawing.Filed June 18, 1962, Ser. No. 202,952 7 tillaims. (Cl. 260-23) Thisinvention relates to the stabilization of polyolefin compositions. Moreparticularly, this invention relates to the stabilization of polyolefincompositions against deterioration resulting from exposure to sunlightor ultraviolet light by the incorporation therein of an alkylnaphthoate.

Thermoplastic compositions have found wide acceptance as usefulmaterials for making films, foils, fibers, filaments and other articles.These articles are inherently strong, dimensionally stable, relativelyinert to common household solvents and are easily colored for anattractive appearance. However, it is known that such compositions andarticles produced therefrom are subject to rapid and severe degradationand discoloration when exposed to elevated temperatures and to light,particularly ultraviolet light. The problem is extremely serious whensuch polymeric compositions are thermally fabricated into fibers to beemployed in window curtains, automobile seatcovers, and the like, whichare exposed for prolonged periods of time to relatively hightemperatures and to direct sunlight. It has become common to incorporatecertain additives into the composition as heat stabilizers and as lightstabilizers to overcome this instability.

A number of ultraviolet light inhibitors are known which inhibit thephoto degradation of many polymers, resins, and plastics. However, it isknown that the polyolefin compositions are much more sensitive thanother polymer systems to photo degradation. Many effective stabilizersfor halogen containing polymers, for example, polyvinylene chloride,polyvinyl chloride, and the like, are non-effective stabilizers inpolyolefins. This is due to the fact that stabilizers in halogencontaining polymers function essentially as hydrogen halide scavengerswhile stabilizers for the halogen free polyolefins operate on adifferent principle. Ultraviolet inhibitors which are especially suitedfor cellulosic esters, such as cellulose triacetate, cellulose acetatebutyrate, and the like, are not necessarily effective ultravioletinhibitors for polyolefins, due to the inherently different nature ofthe polyolefins.

Polyolefins, such as polyethylene, polypropylene, and the like, aresubject to photo oxidation when exposed to the sunlight. This oxidationis characterized in its early stages by the breaking of the polymerchain and the formation of carbonyl groups. As the oxidation continuesthe polymer cracks and loses tensile strength to the point of mechanicalfailure.

In the preparation of polyolefin fibers, a uniform dispersion of thestabilizer in the polyolefin is desirable. Therefore, it is necessarythat the stabilizer be blended with the polymer before spinning. Mostpresently known ultraviolet stabilizers are thermally unstable anddecompose during the spinning process. This results in the formation ofundesirable color and/ or the loss of physical properties of the fiber.In order for the ultraviolet stabilizer to be satisfactory for use inpolyolefin compositions it should be thermally stable; it should bestable itself towards ultraviolet light; it must not be colored ordevelop any color during use; and it must be compatible with the polymerused.

It is an object of this invention to provide new ultraviolet lightstabilizers for polyolefin compositions.

It is another object of this invention to provide new ultraviolet lightstabilizers for polyolefin compositions 3,21,27? Patented Nov. 16, 1955which are essentially colorless and will not form color on exposure.

It is a further object of this invention to provide new ultraviloetlight stabilizers for polyolefin compositions which will be effectivewhen used in small concentrations.

It is a further object of this invention to provide new ultravioletlight stabilizers for polyolefin fibers which are thermally stable underthe spinning conditions used to prepare the fibers.

Other objects and advantages of this invention will be apparent from aconsideration of the description of the invention which followshereafter.

In accordance with the present invention it has been found that when analkyl naphthoate is added to a polyolefin composition the alkylnaphthoate acts as a stabilizer against the effects of ultravioletlight.

The alkyl naphthoates used to prepare the compositions of this inventionare compounds having the formula wherein R is an alkyl group containingfrom 4 to 25 carbon atoms. Illustrative of suitable alkyl naphthoatescoming within the scope of the above structural formula are thefollowing: isobutyl naphthoate, hexyl naphthoate, 2,2-dimethyl pentylnaphthoate, heptyl naphthoate, nonyl naphthoate, dodecyl naphthoate,pentadecyl naphthoate, Z-methyl-S-hexyl heptarlecyl naphthoate, eicosylnaphthoate, 2-ethyl docosyl naphthoate, pentacosyl naphthoate, and thelike.

The alkyl naphthoate used in the preparation of the compositions of thisinvention may be present in an amount of from about 0.05 percent toabout 5 percent, based on the total weight of the composition. It ispreferred that the alkyl naphthoate be present in an amount of fromabout 0.2 percent to about 2 percent, based on the total weight of thecomposition.

The alkyl naphthoates may be used to stabilize a wide variety ofpolyolefin compositions against deterioration resulting from exposure toultraviolet light. The olefin polymers and copolymers of this inventionare those obtained by the polymerization of olefins and branched olefinscontaining from 2 to 10 carbon atoms in the monomeric chain.Illustrative of suitable monomers are ethylene, propylene, 1-butene,isobutylene, l-pentene, 4-methylpentene-1, 2-butene, 2-pentene,Z-methylbutene-l, Z-methylbutene-Z, 3-methylbutene-l, 3-ethylbutene-1,1- hexene, Z-hexene, l-heptene, l-octene, 2-octene, 2-methylpentene-l,and the like. Copolyrners of the above-mentioned monomers may also beused for purposes of this invention.

The alkyl naphthoates may be incorporated into the polyolefincompositions by conventional methods used for blending such materialsinto plastics. Illustrative of methods that may be employed are asfollows: melt blending, dry blending, solution blending, sorption of asolution of stabilizer on dry polymer, and the like.

The polyolefin compositions stabilized in accordance with this inventionhave excellent life expectancy and can be used for a wide variety ofuses. The stabilized polyolefins of this invention may be used inoutdoor uses requiring prolonged exposure to the sunlight. Polyolefincompositions stabilized in accordance with this invention can be cast,rolled, extruded or molded into sheets, rods, piping, tubes, fibers andother shaped articles. These compositions may also be used for coatingsuch materials as paper, metal foil, wire, glass fiber fabrics and thelike.

The polyolefin compositions of this invention are especially suited tobe spun into fibers having excellent stabilization against ultravioletlight. These fibers may be manufactured by several methods of spinning,such as melt spinning, dry spinning, and wet spinning.

In the melt spinning method the polymer is heated to a high temperatureuntil it becomes molten and is thereafter forced through sand packs andthe like, and then through spinnerets from which it is extruded.

In the dry spinning method the polymer is dissolved in a suitablesolvent and, subsequently, extruded from spinnerets into a heatedatmosphere in order to evaporate the solvent.

In the wet spinning method the polymer is dissolved in a suitablesolvent and extruded from a spinneret into a coagulating bath capable ofleaching the solvent from the fiber.

The polyolefin compositions of this invention are especially suited forspinning by the melt spinning method. Extremely high temperatures mustbe used in melt spinning and this requires the exercise of extreme carein order to prevent the decomposition of the polymer. Most presentlyavailable ultraviolet stabilizers will decompose when heated to the hightemperatures necessary in a melt spinning operation. It has been foundthat the alkyl naphthoates of this invention will not decompose at thehigh temperatures used in melt spinning.

In preparing polyolefin fibers the alkyl naphthoates are blended withthe polymer before spinning in a conventional spinning process toproduce the fiber. This is necessary in order to obtain a uniformdispersion of the alkyl naphthoate in the polymer. If it is desired touse other additives such as heat stabilizers, anti-static agents,fire-retarding agents, dyes, plasticizers, and the like in the polymersolution, they may be incorporated therein without the danger ofdecomposition or seriously affecting the properties of the end productat any time prior to spinning into the filament formation.

The following example is intended to illustrate the new compositions ofthis invention more fully, but is not intended to limit the scope of theinvention. In the example all parts and percentages are by weight unlessotherwise indicated.

Example Slurry A was made by placing 700 grams of powdered polypropylenein a Waring Blendor and adding thereto 2 liters of n-hexane. A heatstabilizer consisting of 2.8 grams of Tyox (dilauryl thiodipropionate),2.1 grams of Santowhite [4,4-butylidene bis(6-tert-butyl-m-cresol)],1.05 grams of zinc stearate, and 1.05 grams of Polygard[tris(nonylphenyl) phosphite] was slurried in 250 ml. of n-hexane in abeaker and 3.5 grams of 2,2-dimethyl pentyl naphthoate were added tothis slurry. This stabilizer slurry was then added to slurry A. Thebeaker used in the preparation of the stabilizer slurry was washed with50 ml. of n-hexane and the washings were also added to slurry A. Theresulting slurry was then blended for 15 minutes. The n-hexane presentwas removed by evaporation and the residue was dried at 65 C. in avacuum oven for approximately 6 hours. The dry polymer obtained was thenblended for 3-0 minutes. The polymer was found to have a whiteness valueof 100. The test employed to determine this value consisted ofdeterminations on the proximity to complete whiteness, i.e. 100, byreflectance measurements made by using a spectrophotometer. The methodsused were those recommended by the Standard Observer and CoordinateSystem of the International Commission on Illumination as fully setforth in the Handbook of Colorimetry, published in 1936 by theTechnology Press, Massachusetts Institute of Technology.

Fiber was made from the above identified polymer by a conventional meltspinning process. The fiber was spun at a pack temperature of 270 C. anda transition line temperature of 236 C. The fiber was then drawn at atemperature of C. The fiber was found to have a whiteness value of 84.3as defined above.

The fiber was determined to have 62 percent strength retention after anexposure of 30,000 langleys in Arizona sunlight as compared to 48percent strength retention for the unstabilized polymer.

As many variations within the spirit and scope of this invention willoccur to those skilled in the art, it is to be understood that theinvention is not limited to the specific embodiments thereof except asset forth in the appended claims.

We claim:

1. A new fiber-forming composition of matter comprising a polyolefinderived from a mono-olefin containing from 2 to 10 carbon atoms in themonomeric chain and from 0.05 percent to 5.0 percent, based on the totalweight of the composition, of a naphthoate having the formula ii CORwherein R is an alkyl group containing from 4 to 25 carbon atoms.

2. A new fiber-forming composition of matter comprising a polyolefinderived from a mono-olefin containing from 2 to 10 carbon atoms in themonomeric chain and from 0.2 percent to 2.0 percent, based on the totalweight of composition, of a naphthoate having the formula 0 JLOR whereinR is an alkyl group containing from 4 to 25 carbon atoms.

3. The composition of matter as defined in claim 2 wherein thepolyolefin is polypropylene.

4. The composition of matter as defined in claim 2 wherein thenaphthoate is 2,2-dimethyl pentyl naphthoate.

5. The composition of matter as defined in claim 2 wherein thepolyolefin is polypropylene and the naphthoate is 2,2-dimethyl pentylnaphthoate.

6. A new fiber-forming composition of matter comprising a polyolefinderived from a mono-olefin containing from 2 to 10 carbon atoms in themonomeric chain, from about 0.5 percent to about 2.0 percent, based onthe total weight of the composition, of a heat stabilizer comprising atleast one compound selected from the group consisting of dilaurylthio-dipropionate, 4,4-butylidene bis(6-tertbutyl-m-cresol), zincstearate, and tris (nonylphenyl) phosphite, and from about 0.05 percentto about 5. 0 percent, based on the total weight of the composition, ofa naphthoate having the formula wherein R is an alkyl group containingfrom 4 to 25 carbon atoms.

7. A new fiber-forming composition of matter comprising polypropylene,from about 0.5 percent to about 2.0 percent, based on the total weightof the composition, of a heat stabilizer comprising about 40 percent ofdilauryl thiodipropionate, about 30 percent of 4,4'-butylidene bis(6-tert-butyl-m-cresol), about 15 percent of zinc stearate, and about 15percent of tris (nonylphenyl) phosphite, each percent being based on thetotal weight of the stabilizer, and from about 0.2 percent to about 2.0

5 6 percent, based on the total weight of the composition, of 3,069,36912/1962 Galbraith et a1 260-45.85 2,2-dimethy1 pentyl naphthoate.3,125,597 3/1964 Wahl et a1 26045.85

References Cited by the Examiner FOREIGN PATENTS UNITED STATES PATENTS 51,229,088 3/1960 France. 2,733,226 1/1956 Hunter 260 45.7 OTHERREFERENCES 2 9 5 17 5 19 1 salyer et a] 5 5 Chemical Abstracts, v01. 46,1952, p. 7812(h) which 1s 3 022 2 2 19 2 Armitage et 1 5 an abstract OfDutch No. 69,046, Dec. 15, 1951. 3,033,814 5/1962 Tholstrup 260-4595 10LEON J. BERCOVITZ, Primary Examiner.

6. A NEW FIBER-FORMING COMPOSITION OF MATTER COMPRISING A POLYOLEFINDERIVED FROM A MONO-OLEFIN CONTAINING FROM 2 TO 10 CARBON ATOMS IN THEMONOMERIC CHAIN, FROM ABOUT 0.5 JPERCENT TO ABOUT 2.0 PERCENT, BASED ONTHE TOTAL WEIGH OF THE COMPOSITION, OF A HEAT STABILIZER COMPRISING ATLEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF DILAURYLTHIO-DIPROPIONATE, 4,4''-BUTYLIDNEN BIS(6-TERTBUTYL-M-CRESOL), ZINCSTEARATE, AND TRIS (NONYLPHENYL) PHOSPHITE, AND FROM ABOUT 0.05 PERCENTTO ABOUT 5.0 PERCENT, BASED ON THE TOTAL WEIGHT OF THE COMPOSITION, OF ANAPHTHOATE HAVING THE FORMULA